Wrap github.com/go-webauthn/webauthn behind the api.PasskeyVerifier
seam so the api package stays free of go-webauthn types. The adapter
covers the credential-creation ceremony only (BeginRegistration /
CreateCredential); the login/assertion path is a deferred slice.
Ceremony state crosses the seam as opaque marshaled SessionData, the
attestation as an io.Reader, and the verified result as a plain
VerifiedCredential. SessionData carries no expiry so the challenge
row's TTL stays the single liveness authority. New rejects an empty
RP id or origin list so a misconfigured deployment fails at
construction rather than minting unverifiable challenges.
Tests drive a real relying party against a virtual authenticator
(descope/virtualwebauthn): a full creation round-trip plus adversarial
guards proving origin-mismatch and user-mismatch are rejected and
already-bound credentials are excluded.
